This invention relates to a bearing assembly including a rotational speed detector for detecting the rotational speed of e.g. a vehicle wheel.
Today's motor vehicles are equipped with various sophisticated control systems including an anti-lock brake system (ABS) for preventing lockup of any wheel of the vehicle during hard braking, a traction control system for preventing slipping of any drive wheel during acceleration of the vehicle, and a car navigation system. In order for these systems to reliably operate, it is necessary to accurately detect the rotational speeds of the respective vehicle wheels. Thus, many of today's motor vehicles include bearing assemblies each carrying a rotational speed detector for detecting the rotational speed of a vehicle wheel.
Such a bearing assembly is disclosed in Japanese patent publication 6-308145A.
The bearing assembly disclosed in this publication includes a stationary outer member having a radially inner surface formed with a plurality of raceways, a rotary inner member having a radially outer surface formed with raceways each radially opposing one of the raceways of the outer member, and a plurality of rolling elements disposed between the radially opposed raceways. The rotary inner member carries a pulse generator, and the stationary outer member carries a sensor arranged to face the pulse generator.
The sensor is snap-fitted to an annular sensor holder fitted on the outer member at its inboard end by pressing.
The sensor holder comprises an annular ring portion fitted on the outer member at its inboard end, and a frame-shaped pocket into which the sensor can be snap-fitted. The pocket includes a clip portion that elastically presses the head of the sensor when the sensor is snap-fitted in the pocket, thereby retaining the sensor in the pocket.
Such a snap-fit type sensor holder is made of steel and is electrogalvanized for improved corrosion resistance. But such an electrogalvanized sensor holder tends to suffer from corrosion at its clip portion after long use. If the clip portion is broken due to corrosion, the sensor may separate from the wheel bearing assembly.
An object of the present invention is to provide a wheel bearing assembly which can reliably prevent separation of the sensor.